1. Field of the Invention
The present invention relates to an image projector which is small in size and has improved portability, and an image correction method.
2. Related Background Art
Laser displays have been proposed which directly scan a projection screen with a laser light beam by using projection means such as an optical deflector, e.g., a polygon mirror or a galvanometer mirror to display a television image or the like. This type of display device is incapable of direct modulation in the case of high-resolution display because the light source used therein is a gas laser. There is a need to perform modulation of light output from the laser light source by using a high-priced electro-optic or acousto-optic modulator. Also, the scale of the display device is large and a screen must be set in a fixed position.
Laser displays have recently been proposed in which a semiconductor light emitting device such as a laser diode or a light emitting diode (LED) capable of direct modulation is used as a light source, and in which a micromirror is used as an optical deflector. FIG. 1 shows a configuration of a laser display apparatus using a semiconductor light emitting device. The laser display shown in FIG. 1 is constituted by a light source modulation drive unit 100, a direct-modulation light source 101, a first optical deflector 102, a second optical deflector 103, an emergent-beam-correction optical system 104, and a projection surface 105. The display apparatus thus arranged can be reduced in size and in cost because there is no need to use an optical modulator.
As an example of the micromirror used in this arrangement, an ultraminiature optical deflector having a square mirror about several millimeters per side will be described which has been realized by a technique for working a semiconductor material, i.e., silicon, which is called micromechanics (Japanese Patent No. 02722314). FIG. 2 shows a micromirror made by using the micromechanical technique. The micromirror shown in FIG. 2 is constituted by a silicon substrate 200, a movable plate 201, torsion bars 202, a planar coil 203, a mirror 204, an electrode terminal 205, and permanent magnets 206. This micromirror is of an electromagnetic type such that a drive current is caused to flow through the planar coil 203 and the Lorenz force between the planar coil 203 and the permanent magnets 206 is utilized as a drive force. A number of electrostatic or piezoelectric micromirrors have also been proposed. It is possible to realize a laser display reduced in size and in power consumption by the semiconductor light emitting device and the micromirror described above.
It is conceivable that an image projector smaller in size and having improved portability, e.g., one of the above-described image projectors, unlike stationary types, is used to project light in any of various forms onto an object which reflects light (hereinafter referred to as xe2x80x9cscreenxe2x80x9d). A situation is also conceivable in which the image projector performs while the positional relationship between the screen and the image projector is being changed. In such a situation, there is a need to adjust a projected image according to the positional relationship between the screen and the image projector. More specifically, there is a need to adjust the size of the image area and the focal distance according to the distance between the screen and the image projector. There is also a need to correct the shape of the image area according to an inclination or a curvature of the screen. However, it is difficult to perform such automatic correction in the above-described image projector.
In view of the above-described circumstances, an object of the present invention is to provide an image projector:
(1) having a function of automatically adjusting a size of an image area and a focal distance corresponding to a distance between a screen and a image projector, and
(2) having a function of automatically correcting a shape of the image area corrresponding to an inclination or a curvature of the screen, and
(3) simpler in structure, reduced in size and in weight, and having improved portability,
and a method for correction in the image projector.
To attain the above-described object, according to one aspect of the present invention, there is provided an image projector comprising: a light source having means for modulating light for forming an image, a measuring light source for supplying measuring light, a mixing optical system for mixing the light for forming an image and the measuring light on one optical axis, an optical deflector for scanning the light mixed by the mixing optical system and projecting the light onto a screen, a photodetector for detecting the measuring light reflected on the screen, and correction means for correcting an image by controlling the projected light on the basis of the result of detection performed by the photodetector.
According to another aspect of the present invention, there is provided an image projector comprising: a light source having means for modulating light for forming an image, an optical deflector for scanning the light for forming the image and projecting the light onto a screen, a photodetector for detecting light reflected on the screen, and correction means for correcting an image by controlling the projected light on the basis of the result of detection performed by the photodetector.
According to still another aspect of the present invention, there is provided an image correction method comprising: scanning light for forming an image by an optical deflector and projecting the light onto a screen, detecting light reflected on the screen by using a photodetector, and correcting the image by controlling the projected light on the basis of the result of detection using the photodetector.
According to a further aspect of the present invention, there is provided an image correction method comprising mixing light for forming an image and measuring light on one optical axis by means of a mixing optical system, scanning the mixed light by an optical deflector and projecting the light onto a screen, and correcting the image by controlling the projected light on the basis of the result of detection using the photodetector.
The above points are the features of the present invention, and details and functions thereof will be described below.